Imaging tables for supporting a patient for medical diagnostic imaging purposes are well known. Tables of this type are shown and are described, for example, in U.S. Pat. No. 4,541,108 to Grady et al, U.S. Pat. No. 5,048,071 to Van Steenburg, and U.S. Pat. No. 5,237,600 to Kamata. These devices include a stationary base anchored to the floor of an examination room, a vertical column extending upwardly from the base, and a radiolucent table top and table top support structure extending laterally from the column, so that the patient is supported in cantilevered fashion. The table tops in all of these references can be raised and lowered. The devices shown in two of these patents, i.e., U.S. Pat. No. 4,541,108 and U.S. Pat. No. 5,048,071, also permit the table top to be tilted about a transverse axis to effect Trendelenburg tilting between a head high position and a head low position. The apparatus of U.S. Pat. No. 5,048,071 also provides for tilting of the patient support table top about a longitudinally extending axis. It is necessary to provide a stationary base anchored to the floor in the foregoing devices because the patient is supported in a cantilevered fashion and is not directly above the base. The footprint of the table top in the above references lies outside the base.
The foregoing structures suffer significant disadvantages. First, medical personnel do not have 360.degree. access to the patient around the entire perimeter of the table top. The side arm that supports the table top is in the way. Second, the stationary base requires a dedicated imaging room with a dedicated floor area for the base. Flexibility is lacking. Third, it is not possible to use a table top having uniform radiolucency. Greater strength is required in the region where the table top is supported, and greater strength is achieved only at the expense of radiolucency. Greater radiation intensity (KV), sufficient to cause penetration in the less radiolucent portions of the table top, is required.
Medical imaging tables having structures as described above have been preferred for various reasons. U.S. Pat. No. 4,541,108 states that a mobile x-ray cannot be tilted, but rather requires that the patient be supported only in a horizontal position. Consequently, a stationery base is deemed necessary. U.S. Pat. No. 5,048,071 refers to devices in which an imaging table is supported either translatively or fixably above a base column, but warns that such arrangements pose problems because supporting tubes, hoses and monitoring lines may become tangled, kinked or pulled loose from a patient, or because access by members of the medical team or radiological examination of any desired portion of the patient's body may be obstructed. Consequently, the table top for supporting the patient is supported off to the side, which requires a stationary base for stability.
Another deficiency of the foregoing devices is that they offer only a single table top. As result, those devices offer no versatility, since no single table top dimensions or configurations are preferred for all diagnostic imaging procedures.
A mobile imaging table comprising a base, a column, and a vertically liftable and longitudinally tiltable table fixedly mounted on a support plate or pedestal directly above the base is available from Beta Medical Products, Inc. of Akron, Ohio (the assignee of the present invention). This imaging table, Model S4008, is described in a brochure captioned "Beta 90/50 Mobile Imaging Table EP Configuration - Model S4008". The support plate and table top mounted thereon can rotate about a transverse axis from +85.degree. (85.degree. in one direction from the horizontal, e.g., head high) to -30.degree. (30.degree. in the other direction from the horizontal, e.g., head low). This imaging table has a single table top. This apparatus can support a weight (i.e., a patient) up to 400 pounds.
An imaging table which includes interchangeable table tops has been advertised and offered for sale under the name of "FasTABLE" in the United States and elsewhere by Diasonics, Inc, (international) of Milpas, California and by OEC-Diasonics of Salt Lake City, Utah. The table therein shows a stationary base, a column extending upwardly from the base, a table top support mechanism extending laterally from the column, and a series of table tops, including a first table top for radiology applications, a second table top for intraoperative applications, and a third table top for urology and gynecology applications. The table top can be raised and lowered, and it can also be rotated longitudinally (a .+-.30.degree. Trendelenburg-reverse Trendelenburg rotation) and laterally (.+-.20.degree.). This table suffers from the same disadvantages as the other tables having table tops supported outside the base, which have been discussed above.